It is common knowledge that metadata defined illustratively in SMPTE 298M or 335M (Society of Motion Picture and Television 298M, 335M) is used as supplementary data added to video and audio signals picked up by video cameras or the like (referred to as video and audio materials, or called material data collectively hereunder).
The metadata is made up of diverse kinds of information about material data, such as titles of video and audio materials, types of the titles, scene numbers, take numbers, and video sources (e.g., video camera); attributes associated with the material data such as storage locations and sizes; and contents of the materials.
When prepared for transmission, the metadata is written into a user data word (UDW) allocated in an ancillary data packet ANC in SDI (serial digital data interface) format.
The above-mentioned metadata includes ID (unique ID information) defined in ISO (International Organization for Standardization)/SMPTE 330M. The ID information is defined as UMID (Unique Material Identifier) that identifies each item of material data in a manner that is unique in the world. When used as the globally unique ID for each material data item, the UMID is quite effective in searching for and matching desired material data.
Japanese Patent Laid-Open No. 2002-297628 discloses a technique of searching for information by effectively utilizing UMID.
The material data obtained by means of a video camera or like equipment is finished usually as a single video content following various editing processes. That is, after the pick-up by the video camera or the like, the material data undergoes such diverse processes as encoding, decoding, editing, and re-encoding.
Japanese Patent Laid-Open No. 2000-59788 discloses a technique of utilizing the compression parameter destined for encoding in such a manner as to minimize the degradation in picture quality that may occur during re-encoding.
Compressed material data is edited usually in the following sequence: compressed material data is first provided by the video camera or the like. At the editing stage, the compressed material data is decoded into a baseband signal. The material data is then edited in the baseband signal format. Thereafter, the signal is re-encoded to restore the compressed material data.
The processes involved are repetitive: the material data is first decoded for editing purposes. After the editing, the data is again encoded. The process iterations tend to degrade picture quality. This is the problem that is supposed to be suppressed by the technique disclosed in Japanese Patent Laid-Open No. 2000-59788. More specifically, the disclosed technique involves adding the compression parameter destined for initial encoding to the material data that is transmitted. After the transmission and subsequent editing, the material data is suitably processed when again encoded using the compression parameter employed during the initial encoding, whereby the degradation in picture quality is prevented.
To let previous processing parameters be known requires transmitting material data together with its corresponding processing parameters used in the past. Adding any processing parameters to the material data destined for transmission signifies an increase in the amount of data to be sent. Conversely, to suppress the increase in data size requires minimizing the processing parameters to be added to the data, which inevitably results in a deterioration in picture quality.
Adding the past processing parameters to the material data to be transmitted permits subsequent data processing with a minimum of picture data degradation. But this procedure necessarily entails an increased load on the process of data transmission. On the other hand, attempts to reduce the burdens on data transmission involve adding as few processing parameters as possible to the target data, which leads to diminished effectiveness in preventing picture quality deterioration.